Hansensolubility

Hansen solubility parameters (HSP) are a set of three cohesive energy density parameters used to describe and predict solubility and compatibility of materials. They decompose solvent–solute interactions into distinct contributions: dispersion (δd), polar (δp), and hydrogen-bonding (δh). Each substance has a point in Hansen space defined by these three coordinates. The overall solubility parameter δT is the vector magnitude δT = sqrt(δd^2 + δp^2 + δh^2). To compare two substances, the Hansen distance Ra is used: Ra = sqrt(4(δd1 − δd2)^2 + (δp1 − δp2)^2 + (δh1 − δh2)^2). A smaller Ra relative to a substance’s interaction radius Ro suggests greater solubility or miscibility between the pair.

Applications of HSP include predicting solvent effectiveness for dissolving polymers, pigments, or resins; guiding formulation of coatings, adhesives, and lubricants; and assisting in polymer design and compatibility studies. Typical practice involves obtaining or estimating the δd, δp, and δh values for solvents and solutes from experimental data, group-contribution methods, or trusted databases; polymer values are often estimated from monomer units. Software tools and empirical correlations are commonly used to compute Ra and Ro for practical screening.

Limitations exist: HSP provide a simplified, often approximate, view of solubility and may not capture specific interactions, temperature dependence, or complex mixture effects. The method works best as a screening tool rather than a definitive prediction, and reliable data for δ values are essential. Nonetheless, Hansen solubility parameters remain a widely used framework for assessing solubility trends and guiding material selection.